Thermostatic switch mechanism



May 30, 1939. s. ZURCHER THERMOSTATIC SWITCH MECHANISM Filed Feb. 15, 1937 1% w W m P x o at vsfA n n P Patented May 30, 1939 UNITED STATES THERMOSTATIC SWITCH MECHANISM' Ernest Zurcher, Knoxville, Tenn, assignor to General Electric Company, a corporation of New York Application February 15, 1937, Serial No. 125,872

8 Claims.

This invention relates to switch mechanisms, particularly to switch mechanism operated automatically in accordance with variations in a predetermined condition such as temperature or the 6 like. The invention is 01 particular advantage in thermostatic control switches of the rod and tube actuated type.

One of the objects is to provide an improved 7 form oi snap action switch mechanism capable of 10 being mounted on a base in either of two reversed operating relations with respect to an operating arm which is actuated in accordance with the variations in temperature or other predetermined condition. This permits the switch mechanism ,to

1' be used either to open-or to close a circuit upon a predetermined variation in the temperature or other condition.

A further object is to provide improved means for adjustment of the'diiierential oi the snap ac- 20 tion switch mechanism as well as adjustment of the value of temperature or other condition at which the switch mechanism is to be either opened or closed.

A still further object is to provide an improved 25 form of double switch mechanism for snap action operation at diflerent selected values of temperature or other condition and'having a reversed criss-cross operating relation with a single operating arm actuated by means responsive to tem- 39 perature or other conditions. This enables the entire device to be of minimum size without sacriflcing sensitivity and at the same time provides for ready adiustment of and electrical connection with the switch mechanisms to be made.

Other objects will be pointed out in the description of the accompanying drawing in which Fig. 1 is a perspective view oi a preferred form of thermostatic switch mechanism embodying the im provements oi. the present invention with certain parts cut away or exploded for the sake of clarity,

and Fig. 2 is a view showing the details of construction oi the rod and tube thermostatic operating mechanism.

As illustrated the improved switch mechanism 45 of the present invention is operated by a thermostat of the rod and tube type. The rod ill may be formed of pyrex glass or quartz or other relatively non-expansiblematerial and is carried inside of the tube H which is formed of nichrome steel 50 or other relatively expansible material. The tube II is secured to the nut 12 which is removably threaded into the plate l3 carrying the switch mechanism. The base l5 oi the switch mechanism is preferably formed of molded insulating material 55 and provided with openings it through which the (Cl. filth-137) feet 01' the bracket i! may be inserted and secured in position on the base by suitable fastening means such as the rivets Ill. The bracket I1 is provided with spaced apart bearing notches l9 in which the knife edge pivots of the operating member ii 2| are movably mounted. The bracket l1 and the operating arm 2| have suitable shoulders formed thereon for maintaining the biasing spring 22 in operating relation therebetween.

The operating arm 21 carries an adjustable l0 screw threaded plug 23 which engages with the point of the cap 24 carried upon the end of the rod I0. By rotating the screw threaded plug 23. the position or the operating arm 2! may be adjusted so as to extend in spaced relation with the 15 base l5 and substantially parallel therewith.

The base i5 is provided with suitable seats 25 and 26 on opposite sides of the operating arm 2i upon which the snap action switch mechanism 21 may be mounted in reversed operating relation S0 with the operating arm 2!. This permits the switch to be used with either a single switch mechanism 21 mounted either for circuit opening or circuit closing duty upon a. predetermined temperature chan e or used with double switch mecha- 2o nisms 21 and 50, one on each side of the operating arm 2| for both circuit opening and circuit clos ing duty upon predetermined temperature variations as will be pointed out more fully hereinafter.

'The switch mechanism 21 is of the magnetic 3i} snap action type. It consists of a supporting arm having a central channel portion 29 with the arms 30 and 31 extending in opposite direction from the legs oi the channel. The end of the leg; 3i is provided with suitable mounting openings for receiving the fastening screw 32 whereby the end of the arm 3| is fixedly mounted upon the base l5.

At the end of the supporting arm 30, the resilient switch arm 35 is mounted by means of the rivet 30. The resilient arm 35 preferably is formed in two superposed sections with the section 37 of greater resilience than the section 38. Both sections of the arm 35 extend through the channel portion of the support 29 and the magnetic arms.- ture 38 is carried upon the section 38 and the contact 40 is carried upon the section 37 with the stem of the contact 40 extending through a suitable opening formed in the end oi the section 38. The permanent magnet 63 is mounted upon the arm 3i in snap action cooperating relation with the magnetic armature It will or: observer: that the section of the arm 3i is weakened adjacent the mounting end thereof by provision of ac weakening notches it which are located in substantial alignment with the contact 40. The contact 45 is arranged to be adjustably mounted on the base l5 so as to extend between the contact 40 and the arm 3| in substantial alignment with the weakening notches 44. The contact 45 is carried upon the arm 46 which is provided at the end thereof with suitable openings for receiving the securing screws which mount the contacts in reversed position on one of the seats or 26 with the end of the supporting arm 28 mounted upon the other one of the seats 25 or 26.

The switch mechanism 5i! is identical in construction with that of the switch mechanism 21 as just described.

With the two switch mechanism 27 and 53 mounted in reversed position on the base t5, the two switch arms thereof extend in spaced apart criss-cross relation on opposite sides of the free end of the operating arms 28 in operating relation therewith. By adjusting the screw5 i the supporting arm 3| may be flexed about the section weakened by the notches 44 so as to adjust the switch arm 35 to a desired position in the path of the operating arm 2!.

.Since the contacts and are in substantial alignment with the section weakened by notches 44, this adjustment of the arm 3i does not materially vary the operating relationship between the magnet 43 and the armature 39 and the con.- tacts 40 and 45. Thus with the contact 35 adjusted to provide the desired differential in the snap action of the switch arm 35, this adjustment is not materially disturbed.

By similar adjustment of the screw 52, the position of the switch arm 35 of the switch mechanism may be varied so as to be engaged and disengaged by the operating arm N at different values of temperature.

The operation of the thermostatic switch shown in Fig. 1 is as follows. Upon increase in temperature, the tube ll lengthens without, however, any appreciable lengthening of the rod ill. This permits the spring 22 to move the operating arm 2! toward the base i5. By suitable adjustment of the switch mechanism 27, the movement of the operating arm 2i towards the base i5 may be made to close'the contacts thereof at a desired value of temperature and with a snap action. As the movement of the operating arm 2i towards the base continues, the switch mechanism to may be adjusted so as to open the contacts thereof at a desired value of temperature and with a snap action. A

When the temperature varies in the opposite direction, the tube ll shortens and through the agency of tube 10 moves the operating arm 2i away from the base Hi. This movement will first close the contacts of the switch mechanism 56 with a snap action and then open the contacts of the switch mechanism 2'! with a snap action. In each case the differential between the opening and closing of the switch contacts is determined by adjusting the position of contact 55 to vary the distance between the permanent magnet and the armature 39. This differential adjustment is obtained by means of the adjusting screw 41 which moves the free end of arm 4t carrying contact 45.

With the improved switch mechanism oi the present invention all the electrical circuit connec' tions to the switch mechanism may be made by means of conventional conductors and binding screws as illustrated, the terminal being readily accessible to facilitate such connections. Likewise, the screw adjustments for differential setting as well as temperature setting of the snap action switches are readily accessible and easily made. Thus the improved switch mechanism may be adapted for various applications in temperature control or regulating work. It is particularly well adapted for warm air furnace control in which one of the switches controls the operation of a motor driven air circulating blower and the other switch serves as an excess temperature safety switch.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an automatic device having an operating arm movable in accordance with variations in a predetermined condition, a movable current carrying switch member having a snap action mechanism connected therewith, a separate stationary current carrying switch member for cooperating with said movable switch member to control a circuit, and a base secured to said device and provided with separate means including an adjustable element for mounting each one of said switch members in reversed adjustable positions on opposite sides of said operating arm with said movable switch member in the path of said operating arm and in reversed adjustable operating relation therewith with respect to variations in said predetermined condition.

2. In combination, an automatic device having an operating arm movable in accordance with variations in a predetermined condition and provided with means for adjusting the movement said arm with respect to said va' clone, a snap action switch mechanism including a movable switch member having a contact at one end thereof and a current conducting support connected thereto at the other end thereof and e? tending in. opposing relation with the con end thereof and provided with cooperating s action magnetic means carried between switch member and said support and a separate stationary switch member having a contact cooperating with said first contact to control a circuit, a base secured to said device and provided with separate means for mourn mg the said stationary member and said support or movable switch member on each side of said operating arm with said movable switch member in the path of said operating and in reversed operating relation therewith, means for adjusting the position of said support to vary the position or said movable switch member with respect to said arm in each relation, and separate means for adjusting the position of the contact of said stationary switch member with respect to the contact of said movable switch member for adjusting the differential of said switch member in each relation.

3. In combination, an automatic device having an operating arm movable in accordance with variations in a predetermined condition, a snap action switch mechanism having an adjustable supporting arm and a movable switch member and a separate contact element mounted in cooperating circuit controlling relation ercon, and a base provided with a air of spaced apart supports for movably mounting said operating arm therebetween and for separately and reversely mounting said separate contact element and said adjustable support ng arm with movable switch element on opposite sides oi said operating arm in reverse adjustable circuit controlling relation with respect to variations in predetermined condition.

4. In combination, a base, a pair of duplicate switches reversely mounted on said base and each having an operating member extending in spaced apart criss-cross relation with the operating member of the other, and operating means for said switches including a movable arm having one end thereof extending between the overlapping portions of said switch operating members and in reverse operating relation therewith and the other end thereof movably mounted on said base.

5. A selective circuit controlling switch mechanism having in combination, a base, a pair of duplicate contacts mounted in reverse position on said base and in spaced apart relation, a pair of duplicate switch arms movabiy mounted in re versed position on said base with the operating portion thereof in opposing spaced apart crisscross relation and each extending into circuit controlling relation with the corresponding one of said pair or contacts, and operating means (or said switch arms having a movable element operating in the space between said first pair of contacts and between the overlapping operating portions of said switch arms and in reverse operating relation therewith.

6. In combination, a base, an automatic condition responsive device having an operating arm mounted adjacent one end of the base and extending in spaced relation with the base, a pair of switch mechanisms mounted on the base on opposite sides of said operating arm and having movable switch arms adjustable in spaced crisscross relation with said operating arm extending therebetween in operating relation therewith.

7. In combination, an automatic condition responsive device having an operating arm movable in accordance with variations in a predetermined condition, a supporting arm fixedly mounted at one end and provided with a weakened section adjacent said mounting, a resilient switch arm mounted at the other end of said supporting arm and extending through the path of movement oi said operating arm in operating relation therewith, means for adjusting the other end of said supporting arm to position said resilient switch arm with respect to said operating arm, cooperating magnetic means carried by said supporting arm and said switch arm for providing snap action operation of said switch arm, and a contact adiustably mounted in alignment with the weakened section of said supporting arm in cooperating relation with said switch arm to determine the diflerential in the operation thereof. 8. A switch mechanism having in combination, a channel support with a projecting arm extending from each leg thereof and with said arms extending in opposite directions and provided with mounting means at the end of one of said arms and position adjusting means at the end of the other arm, a resilient switch member mounted at the end of said other of said arms and extending throughthe channel support, cooperating magnetic means carried by said one of said arms and said resilient switch member for providing snap action thereof, an adjustable con tact cooperating with saidresilient switch member to adjust the differential in the snap action operation thereof. and an automatic device having an operating arm movable in accordance with variations in a predetermined condition and extending into operating relation with said resilient switch member.

ERNEST ZURCHER. 

